1. Field of the Invention
The present invention relates to a circuit breaker, more particularly, to a withdrawable-type circuit breaker which has an enhanced safety in a withdrawing operation.
2. Description of the Conventional Art
In general, a circuit breaker is a device configured to pre-detect an abnormal current which may occur in an electric circuit, and to forcibly cutoff an electric path between a power supply side and a load side.
Such a circuit breaker is classified into a fixed-type breaker which is fixedly disposed within a panel of a distribution board and a withdrawable-type breaker which has a main body disposed in an outer box, called a cradle, in an insertable and withdrawable manner so that maintenance and handling may be simply and easily performed.
FIG. 1 is a schematic view illustrating a state that a main body of a circuit breaker is located in a connected position (operation position), and FIG. 2 is a schematic view illustrating a state that a main body of a circuit breaker is located in a test position.
Referring to FIGS. 1 and 2, a cradle 14 includes outer box terminal parts 12 for connecting an electric path of a power supply side to an electric path of a load side of an external power system circuit, and a circuit breaker main body 10 (hereinafter, referred to as “a main body”) includes main body terminal parts 15 at one side of a circuit breaker main body frame 11 (hereinafter, referred to as “a main body frame”) and is connectable to the outer box terminal parts 12.
The main body 10 may be configured to be located at one of a connected position (or a service position, refer to FIG. 1) to connect an electric path of a power supply side of an external power system circuit and an electric path of a load side by being transferred and connected to the outer box terminal parts 12 of the cradle 14 by a separate transfer device 13; a test position (refer to FIG. 2) for testing a connected operation and a disconnected operation of the main body 10, under a separated state from the terminal parts 12 so that a connection to the main circuit is cutoff, but under a connected state to a control power line; and a disconnected position in which a connection to the control power line and the outer power system circuit is cutoff.
FIG. 3 is a partial enlarged view illustrating a conventional circuit breaker in which a connection spring is discharged within a main body, and FIG. 4 is a partial enlarged view illustrating a conventional circuit breaker in which a connection spring is charged within a main body.
As shown in FIGS. 3 and 4, the circuit breaker 10 includes a connection spring 2 which is configured to execute a connection operation of the circuit breaker.
Referring to FIGS. 3 and 4, a connection operation of the circuit breaker will be described.
As shown in FIG. 3, a user rotates a cam assembly 5 in a clockwise direction using a manual charging handle or a charging motor, so that a crank assembly 4 can be rotated in a clockwise direction by a connection structure (a cam-follower structure) of the cam assembly 5 and a drive crank assembly 4.
Referring to FIG. 4, the cam assembly 5 is rotated until it is stopped by a closing latch 6, and the connection spring 2 accumulates an elastic force for a connection operation of the circuit breaker by being compressed by the drive crank assembly 4.
The closing latch 6 is configured to restrict an amount of rotation of the cam assembly 5 when the connection spring 2 is charged (the term “charge” in the description means that the connection spring 2 is compressed to accumulate an elastic force therein for a connection operation of the circuit breaker).
The circuit breaker is configured to execute a connection operation using an elastic force accumulated in and then released from the connection spring 2.
In such a withdrawable-type circuit breaker, the main body 10 can be completely withdrawn to outside of the cradle irrespective of a charging, a connection, or a breaking state of the circuit breaker.
Meanwhile, when a connection button is pressed by a user's erroneous operation in a case where the main body is withdrawn to outside of the cradle in a compressed state of the connection spring, a connection operation is executed while the elastic force accumulated in the connection spring 2 is discharged.
Due to such an operation, a user may be astonished by noise generated by the connection operation or a secondary safety accident may occur.
FIGS. 5 and 6 illustrate open and connected states of the conventional circuit breaker.
The circuit breaker mainly includes a mechanical part 21, a frame 22, a main circuit movable part 23, a main circuit fixing part 24, and a mechanical part driving shaft 27, a mechanical part driving link 25 and a main circuit driving link 26 which are configured to connect the mechanical part 21 and the main circuit movable part 23 to each other.
In a state that the circuit breaker is open, the connection spring 2 is charged by a manual or electrical operation, and the mechanical part 21 is driven by the charged connection spring 2. The mechanical part driving unit 27 is configured to connect the mechanical part 21 and the main circuit movable part 23 to each other, the main circuit movable part 23 and the main circuit fixing part 24 are connected to each other when the circuit breaker is in a connected state.
Under such a configuration, a connected state of the circuit breaker is maintained, and an electric conduction may be possible. Further, when a fault current or a disconnection occurs, the circuit breaker performs a trip operation by an electrical signal and the mechanical part 21 to thus prevent any possible accident.
Referring to FIG. 6, in a connected state of the circuit breaker, since the compression spring 28 is compressed, a downward trip load is generated. The trip load is maintained without being discharged, unless a fault current is generated at the circuit breaker or the mechanical part is intentionally operated.
FIGS. 7 and 8 illustrate a discharged state and a charged state of an open spring of the mechanical part 21 of the circuit breaker.
As shown in FIGS. 7 and 8, a compression spring 28 of the main circuit part and the open spring 33 of the mechanical part are maintained in a charged state under a connected state of the circuit breaker.
When a user performs an open operation by manually or an electromotive force, the mechanical part driving shaft 27 is rotated in a counterclockwise direction and thus the open spring 33 is operated in a discharged state.
Meanwhile, it should be noted that the main body must not be inserted into or withdrawn from the cradle when the circuit breaker is in a connected state. In a case where the main body is withdrawn to outside in a connected state, if an open button is pressed by a user's mistake in a state that the main body has been withdrawn or is being withdrawn, an accident may occur to the user while energy, i.e., an elastic force accumulated in the open spring 33 of the mechanical part 21 and the compression spring 28 of the main circuit part, is discharged out.